26 Jun
2021
26 Jun
'21
2:09 p.m.
On 2021-Jun-26, at 10:15 AM, Paul Koning via cctalk wrote:
A couple years ago, somewhat on a whim, I checked a small number of USB-Serial converters
for driving a couple of Model 28 Teletypes.
I didn't really expect anything so modern to work below 300 BPS, or do the needed
5-data/2-stop, but the teletypes were 75 BPS, which is just another in the division-of-2
series down from 19200,9600,etc.; and I was actually figuring on just using 8-bit and
ensuring the later bits were 0 so they would be seen as stop bits, and take a bit of a
penalty on the 28 print speed (might be a little rough/abusive on the teletype commutator
start/stop though).
Sometimes, ya luck out: one of them actually worked down to 75 BPS, *and* did
5-data/2-stop.
There's no ID on the physical unit but it shows up on the system (OSX) as:
Product ID: 0x2303
Vendor ID: 0x067b (Prolific Technology, Inc.)
(Product ID 0x2303: Prolific produces a series of PL2303x USB-Serial chips.)
It was plug-n-play on the Mac (given a terminal app program that knows to accept and
perform the little-used config specs).
There are some other teletypes to get going that need slower speeds, for which I intend a
solution as (Paul) suggests, bit-banging out of an RPi. The code was written some time
ago, but haven't gotten around to the physical connections.
On Jun 26,
2021, at 11:31 AM, Tapley, Mark B. via cctalk <cctalk at classiccmp.org> wrote:
At one point FTDI had a reasonably good reputation, and I own one of those devices based
on that reputation. I have used it with no obvious problems connecting a TRS Color
Computer 3 to an iMac G3 for a floppy-drive emulator (DriveWire on the iMac), but I think
only for that application so far.
Are there any particular pitfalls I should watch out for with the FTDI device, when/if I
can get back to working with it?
I once bought a USB serial port device with a DE-9 connector on it, Belkin I think. It
worked somewhat. Might have needed its own driver, which on a Mac is highly unusual. It
gave me enough trouble I set it aside.
Since then I've bought several different flavors of the FTDI USB serial device, one
RS-232, one 5 volt logic, one 3.3 volt logic (the latter two with 6-pin connectors to fit
onto pin headers such as are found on the BeagleBone Black). They have always worked
flawlessly (on my Mac), at a number of data rates: 4800, 9600, 19.2k, 115k. I'll
admit I haven't needed stranger cases like 5 or 6 bit data, or exotic slow speeds. As
I mentioned, if that need arises and FTDI isn't good enough I'll have the RPico to
do the job.